The mechanism by which carcinogens selectively interact with cellular organelles in normal and regenerating liver will be investigated in the rat. This will include an examination of various hepatocarcinogens, such as urethan and N-2-acetylaminofluorene, to perturb replicative processes associated with the fabrication of ribosomal and messenger RNA as well as the interaction of the carcinogens with the synthesis of DNA in hepatic nuclei. Other aspects of these studies will include an examination of the effect of carcinogens with the perinuclear membranes of parenchymal and nonparenchymal hepatic nuclei and the associated alterations in these parameters resulting from acute and chronic exposure to carcinogens.